I do, but you're right. However, we're talking about small (one stop or in most cases, much less) differences. My point is that even though it's a relative measurement, labeling the test results as "-7 EV" is pretty darn misleading in light of the specified performance of the cameras being tested. The difference between -2 EV and -7 EV is a 32-fold difference in light intensity.

Isn't the 6D rated at -3ev while the 5d3 is rated at -2ev?So in theory…the 6D should perform better in low light than the 5D3..so why are we surprised?

In good light however, it's a different story. I love my 5D3 in daylight but come night time…the focusing speed is a real downer..especially for a camera that has such good ISO capabilities…Having ISO powers is useless when you can get a focus…i shot a few events at night with it and i constantly miss shots because it fails to focus.Even with a flash, it wont focus fast enough..in fact with the IR on the flash, it became even slower..I seriously hope, as do many others i read, that Canon does release some "fix" to make it focus faster in low light…It's marketed as an event camera but without focusing, you can't shoot any event.

I do, but you're right. However, we're talking about small (one stop or in most cases, much less) differences. My point is that even though it's a relative measurement, labeling the test results as "-7 EV" is pretty darn misleading in light of the specified performance of the cameras being tested. The difference between -2 EV and -7 EV is a 32-fold difference in light intensity.

In fact, he actually tested something close to EV9 (log2(2.8^2*60)=8.88

It's only 7 if you include ISO (log2(2.8^2*60/4)

I get your point, I just often get hung up on little details I find interesting. [/hijack]

I always thought exposure value was independent of sensitivity (i.e. merely a function of f number and exposure time). f/1 for 1 second happens to be EV 0, but EV 0 isn't defined as such.

I think technically he wasn't wrong since EV is something to be defined, but it surely is confusing - that's why af capability in low light should be measured in *lv* which incorporates iso 100 yadayadayada: http://www.kenrockwell.com/tech/ev.htm

Quote

LV 0 LV Zero is defined as the light level that requires a 1 second exposure at f/1 with ISO/ASA100 speed film.

Btw, I asked sometime ago but got no answer - I don't understand why the af capability in low light seems to be independent of the lens used (i.e. open aperture), the metering range does - from the 6d specs:

The test might be useful as a comparison between models, but there is no measured or controlled light level or color temperature. There is no reason to believe that different camera models respond the same to different color temperatures, so a standard temperature removes any arguement about that. Measurements at various color temperatures might be interesting for comparison sake.As to time to focus, its not clear as to how that was measured, I did not notice the methodology. I have found the best way to get to focus is to merely press the shutter button all the way down while the camera is in one shot mode. The camera will take the shot when focus is achieved. Some cameras seem to delay turning on the AF light, but the camera is actually focused earlier. A sensitive mike connected to a oscilloscope can record the shutter button press, and the shutter opening so you get a precise measurement, for example.

Exposure value (EV) is not an amount of light and it also has nothing to do with ISO. It is simply a definition for relating camera settings which are equivalent to each other in terms of how much light they would let in, if there was the same amount of light available.

Setting your camera to f/1.0 and 1 second exposure is still called an EV of 0 even in complete darkness or in bright sunlight. Setting your camera to f/1.4 and 2 seconds exposure is still EV 0.

By telling someone that you are obtaining proper exposure by an EV of 0 and a certain ISO value, then and only then does the actual darkness or brightness of the scene come into play. In that case, changing the ISO will change the EV needed to obtain proper exposure for the same scene. And vice versa, changing the brightness of the scene will also change the EV needed to obtain proper exposure for the same ISO.

So you might ask why then does Canon present on their 6D product page a meaningless specification about sensitivity at -3 EV? EV doesn't mean luminance, but they are acting like it does.

The answer is that it is well-established practice among photographers to express luminance in terms of their camera settings using the EV terminology, by assuming that ISO 100 is used and that a nominally "correct" exposure is being obtained by the camera settings indicated by the specified EV. Since photographers probably communicate best when talking in terms of their camera settings, EV makes for an easy way to understand the level of available brightness for a photographer when this common practice is used.

Anytime exposure value is used to speak of the amount of available light, the assumption is that a CORRECT exposure will be obtained from that EV of aperture/shutter speed AND a sensor sensitivity of ISO 100.

You're adding a lot of confusion here by arbitrarily defining your own zero. It's like saying you're going to start counting everything from the number 4, so if there are of 2 of something on a table, you're telling everyone there are 6. Makes no sense.

Technically, your "0" EV is actually EV = 5. That means your -7 EV is really -2 EV (and in fact, the 6D is spec'd to AF at -3 EV, but of course, that may not equate to real world numbers).

It would help avoid confusion if you restate your numbers according to the real definition of EV = 0, otherwise many people will read that you're testing at "EV = -7" and think you're spewing complete bullsh cow manure.

Sorry, but the fact that you don't seem to understand some of the basics, like the fundamental definition of the basis for the specification you are testing, makes me question what you're doing. I definitely appreciate individual testing (and especially the fact that you did post your definition, so the error could be spotted), but post/blogs like this contribute to the vast and growing pool of bad and/or unreliable information out there.

neuro, i have question on this part: base to my conversion of everything back to iso 100, it shows that- 1/60 f2.8 iso 400 (0) will be equivalent to 1/15 f2.8 iso 100 which is EV 7- 1/60 f2.8 iso 102,400 (-7) will be equalivant to 2 f1.0 iso 100 which is EV -1

is there something wrong with my conversion? however, taking a look into his images, i guess that he was talking about zone system instead of exposure value, but there is no such -7 zone system, and i am scratching my head over here

...The answer is that it is well-established practice among photographers to express luminance in terms of their camera settings using the EV terminology, by assuming that ISO 100 is used and that a nominally "correct" exposure is being obtained by the camera settings indicated by the specified EV. Since photographers probably communicate best when talking in terms of their camera settings, EV makes for an easy way to understand the level of available brightness for a photographer when this common practice is used.

Anytime exposure value is used to speak of the amount of available light, the assumption is that a CORRECT exposure will be obtained from that EV of aperture/shutter speed AND a sensor sensitivity of ISO 100.

+1 helpful nice summary. now can we get back to discussing the 6D's AF performance in terms that make sense and communicate the right story? Lets use the term "EV 0" as it is nearly universally understood in terms of evaluating important camera capabilities.

Ive always been surprised to meet highly intelligent individuals who are completely unable to process the most basic of information, simply because they are too smart to understand the heart of the matter.

I thought the 6D autofocus in -3EV conditions was a one stop improvement over the 5d Mark III and a two stop improvement over the 5D Mark II? I don't know about the Nikon. I don't really get testing beyond the rated limit, maybe I missunderstand further explaination of the -7EV thing would be much appreciated. I also seem to recall a video from DigitalRev (in the boxing ring) where the 5D3 excelled against the D600 no where near -3EV?

I watched that vid ---- it was testing the servo tracking of the 3 though, this is one shot focus mode

I'm always surprised when people put forth results and a conclusion, and then are surprised when others critically evaluate the methods used to generate those results, and weigh the quality of the methods when evaluating the reliability of the results and the strength of the conclusions.

grrrrr..... Ok, I'll say it, I don't really care about the methodology! What I care about is how well this camera's AF performs in a variety of situations. The definition of EV matters less to me than the results! which in this case seem pretty good. I'd like to see more of this!!!

I'm always surprised when people put forth results and a conclusion, and then are surprised when others critically evaluate the methods used to generate those results, and weigh the quality of the methods when evaluating the reliability of the results and the strength of the conclusions.

Something else to think about.

I welcome and appreciate criticism, but how does the discussion of semantics in this test somehow mean that the 6D doesn't focus well in low light?

Some people appreciated the amount of time & energy it took to do this. Some don't. But I do know this:

That center focus square on the 6D is very, very good in low light. Ill grab it before the others for low light situations.

If you cannot walk away from this post/discussion with that very basic, heart of the matter idea, than nothing I can say will matter to you.

I'm always surprised when people put forth results and a conclusion, and then are surprised when others critically evaluate the methods used to generate those results, and weigh the quality of the methods when evaluating the reliability of the results and the strength of the conclusions.